First they told us red meat caused cancer. Then cardiovascular disease. Then diabetes. And now kidney failure. Why eat it at all? I still do, but in moderation.

You have to take studies like this with a grain of salt. There are numerous confounding factors that may invalidate results. For instance, if you’re not Chinese and living in Singapore, results of this study may not apply to you. For another instance, Chinese pork may be different from English, Indian, Canadian, and U.S. pork.

A quote from the article at MNT:

“Researcher Woon-Puay Koh and her team delved into data from the Singapore Chinese Health Study, which included more than 63,000 adults, aged 45-74. They linked the data with the Singapore Renal Registry, which holds the records of all Singapore ESRD patients. The overall aim was to uncover the role of different protein sources on kidney health outcomes.

“We embarked on our study to see what advice should be given to chronic kidney disease patients or to the general population worried about their kidney health regarding types or sources of protein intake,” explains Koh.

In China, the primary red meat is pork, accounting for 97 percent of red meat intake. Other popular protein sources included eggs, dairy, shellfish, fish, soy, legumes, and poultry.

The participants were followed up for an average of 15.5 years. During that time, 951 cases of ESRD [end-stage renal disease] occurred; the resultant data showed a clear trend.

Red meat intake was associated with a dose-dependent increased ESRD risk. Individuals who consumed the highest amounts of red meat – the top 25 percent – showed a 40 percent higher risk of developing ESRD than those who consumed the least red meat – the bottom 25 percent.”

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Red meat and processed meat consumption are associated with “modest” increases in overall mortality and deaths from cancer and cardiovascular disease, according to National Institutes of Health researchers. This goes for both sexes.

Data are from the huge NIH-AARP Diet and Heart Study, a prospective cohort trial involving over 550,000 U.S. men and women aged 50-71 at the time of enrollment. Food consumption was determined by questionnaire. Over the course of 10 years’ follow-up, over 65,000 people died. Investigators looked to see if causes of death were related to meat consumption.

What do they mean by red meat, processed meat, and white meat?

Red meat: all types of beef and pork (wasn’t there a U.S. ad campaign calling pork “the other white meat”?}

Studies like this typically look at the folks who ate the very most of a given type of food, those who ate the very least, then compare differences in deaths between the two groups. That’s what they did here, too. For instance, the people who ate the very most red meat ate 63 grams per 1000 caories of food daily. Those who ate the least ate 10 grams per 1000 cal of food daily. That’s about a six-fold difference. Many folks eat 2000 calories a day. The high red meat eaters on 2000 cals a day would eat 123 grams, or 4.4 ounces of red meat. The low red meat eaters on 2000 cals/day ate 20 grams, or 0.7 ounces.

Comparing these two quintiles of high and low consumption of red and processed meats, overall mortality was 31-36% higher for the heavy red meat eaters, and 16-25% higher for the heavy processed meat eaters. (The higher numbers in the ranges are for women.) Similar numbers were found when looking at cancer deaths and cardiovascular deaths (heart attacks, strokes, ruptured aneurysms, etc).

It’s not proof that heavy consumption of red and processed meats is detrimental to longevity, but it’s suggestive. The “Discussion” section of the article reviews potential physiological mechanisms for premature death.

The researchers called these differences “modest.” I guess they use “modest” since most people eat somewhere between these extreme quintiles. The numbers incline me to stay out of that “highest red and processed meat consumer” category, and lean more towards white meat and fish.

Low carbohydrate diets tend to contain disproportionate amounts of fat from animal sources. Red meathas long been vilified as a major source of saturated fat that some experts believe cause hardening-of-the-arteries (atherosclerosis) via elevations in LDL cholesterol. Others disagree. Poultry, fish ,and shellfish generally have lower amounts of saturated fat than red meat. Would a low-carb diet with a predominance of poultry, fish, and shellfishlead to a more advantageous cholesterol profile?

A 2007 report from U.S. researchers found no lipid advantage to the poultry/fish/shellfish model. In fact, despite high cholesterol and fat intakes, neither diet caused a significant change in total, HDL, or LDL cholesterol levels. Triglycerides fell in both groups, but to a statistically significant degree only on the poultry/fish/shellfish group.

Researchers in Minnesota and Iowa enrolled 18 subjects (6 males, 12 females) between the ages of 30 and 50 who wanted to lose weight. Average body mass index was 31.7, which is mildly obese. The were encouraged to eat an Atkins-style ketogenic diet with a maximum of 20 g carbs/day, providing 1,487 total daily calories, with 7% of calories from carbohydrate, 43% from protein, and 50% from fat. This included two or three cups of salad greens and low-carb vegetables. Three ounces of cheese daily was allowed. Subjects were randomly assigned to eat either red meat or poultry/fish/shellfish. Dietary intervention lasted 28 days.

[This is very similar to Atkins Induction Phase, although Atkins does not limit total calories. The researchers did not say why they wanted to limit total calories.]

Data were not used from six subjects for good reasons (see article). So final data analysis included only 12 subjects.

Results

Both groups lost the same amount of weight: about 5.5 kg (12 pounds) over 28 days.

Average carbohydrate intake was about the same for both groups: 55 g/day.

Average total daily caloric intake was about the same for both groups: 1,380.

The poultry/fish/shellfish group ate 630 mg cholesterol daily, twice as much as the other group. [Eggs and shrimp were popular.]

The difference in intake of saturated fat approached, but did not reach, statistical significance (32 g/day in the red meat group vs 25 g).

Neither diet caused a significant change in total, HDL, or LDL cholesterol levels. Triglycerides fell in both groups, but to a statistically significant degree only on the poultry/fish/shellfish group.

Urine ketones at or above 5 mg/dl were detected on 75% of all dipstick tests.

My Comments

I’m skeptical about the accuracy of the calorie counts. Most people eating Atkins-style take in about 1,800 cals/day. The preponderance of females, however, may explain the unusually low average caloric intake. They didn’t follow their carb restriction very closely, did they? These were free-living subjects not locked in a metabolic ward.

The researchers note that the allowance of cheese in both groups may have sabotaged their efforts for a clear delineation of higher versus lower saturated fat groups.

HDL cholesterol usually rises significantly on low-carb diets. Lack of that here may just be a statistical aberration.

This is such a small study that it’s impossible to draw firm conclusions. Nevertheless, if someone is losing weight on a low-carb diet, it may not matter much from a lipid viewpoint whether they eat a predominance of meat or a predominance of poultry, fish, and shellfish. The study at hand cannot address the long-term consequences of such a choice.